(a) Field of the Invention
This invention relates to a system and process for treating wastewater and more particularly, but not by way of limitation, to a high volume electrolytic water treatment process for greatly reducing various types of contaminates held in suspension in the wastewater and waste streams.
(b) Discussion of Prior Art
Heretofore, previous xe2x80x9cflow-throughxe2x80x9d water treatment processes have had flaws that prevented them from being viable treatments for large, complex and variable waste streams. A particular flaw was the scaling and plugging of electrodes, which plagued the treatment process as the wastewater stream changed in composition. It is possible to develop a treatment scheme that will not plug the electrodes if the composition of the stream remained relatively consistent, but not if the composition varies. Efforts to install elaborate monitoring and control systems have failed when waste stream contaminants coated or blinded sensors, thus rendering the system controls useless. Other methods have been employed to prevent scaling and plugging of the electrodes including polarity reversing and other processing aids. But these methods have proven to be unreliable.
Methods for increasing dwell time for contaminated water in electrode modules and the surface area of the electrodes have been tried by increasing the number of electrode plates in the module or increase the number of modules. But, these optional methods increase the pumping pressure of the water necessary to push the fluid through the electrode modules. The increased water pressure causes extra strain on electrode module gaskets and if the pressure is high enough, leaks and failure of the module may occur. Additionally, in these cases, there is little or no chance for the precipitate to develop or coagulate into bigger particles or for any secondary separation to occur between the modules and electrode plates. The limited coagulation time increases the need for the residence time in the foam removal apparatus and the clarifier in order to allow for the formation of coagulated floc and its subsequent increase in size and density. The designing of a wastewater treatment system to allow for more or less residence time in tanks and clarifiers is very difficult.
In previous xe2x80x9cflow-throughxe2x80x9d electrocoagulation processes, including tubular modules as described in U.S. Pat. Nos. 4,293,400 and 4,378,276 to Liggett, improved removal rates have been shown. The improvements were due to the pre-alignment effect of passing the water to be treated through the electronegative or electropositive backside of the electrodes. These methods served to align the contaminant molecules and ions in the waste stream and made them more susceptible to react as the electrical current or electromotive force was introduced into the waste stream. This electrochemical phenomena is further enhanced by the subject invention by the application of reversing polarity of the direct electrical current current, which provides the electromotive force to drive the electrochemical reaction.
In U.S. Pat. No. 5,587,057 to Metzler et al., an electrocoagulation process is described having electrodes for treating a highly conductive liquid. In U.S. Pat. No. 4,1872,959 to Herbst et al. and U.S. Pat. Nos. 5,043,050 and 5,423,962 to Herbst, the inventor of the subject invention, Robert J. Herbst describes different types of improved electrolytic systems for treating aqueous solutions using conductive conduits and precipitating various organic and inorganic materials suspended in the solution.
None of the above mentioned prior art electrolytic treatment systems for treating liquids disclose the unique features of the subject invention which provides a mechanism for treating high volume, complex and variable waste streams with reliability and functionality not obtainable with other electrocoagulation and flow-through water treatment systems and processes.
In view of the foregoing, it is a primary objective of the subject invention to treat high volumes of waste streams in a range of 1000 to 5000 gallons per minute and greater.
Another object of the invention is the system and process is designed to treat waste streams that are both complex and with variable contaminate compositions.
Still another object of the wastewater treatment system is to greatly reduce contaminate levels in the water using a combination of one or more electrocoagulation modules and one or more flow-through modules.
Yet another object of the treatment system and process is to treat the water first using electrocoagulation modules for effectively handling solids and dropping out solids prior to introducing the resultant fluid to flow-through modules.
A further object of the invention is to use electrocoagulation modules with alternating electrical current for increased floc development time. The increased development time provides for stabilizing and collecting larger and less fragile flocs on the electrodes, thereby providing for ease in removal.
The high volume electrolytic water treatment system for treating wastewater includes pumping influent water to a headworks screen for removing solids in the water. The screened water is then discharged into primary and secondary surge tanks. The tanks include electrocoagulation electrodes. The electrodes, using reversing polarity direct current, destabilize materials such as fats, oils, greases and surfactants. The pretreated influent water is then pumped to one or more elongated flow-through modules. The flow-through modules also include electrocoagulation electrodes for further treating of the influent water. From the flow-through modules, the treated water is sent to a foam removal apparatus and then to a clarifier. Clear water from the clarifier then flows into an effluent weir and discharged from the system thereby completing the water treatment process.
These and other objects of the present invention will become apparent to those familiar with different types of processes and systems for electrolytic, electrochemical or electrocoagulation treatment of high volumes of contaminated water when reviewing the following detailed description, showing novel construction, combination, and elements as herein described, and more particularly defined by the claims, it being understood that changes in the embodiments to the herein disclosed invention are meant to be included as coming within the scope of the claims, except insofar as they may be precluded by the prior art.